hi there
To be honest I do not know when exact I bought the two cartridges but certainly not longer then 3 months.
As I said before I do not print that much.
I did everything you advised me to do in point 1 to 6.
The status now is Color HP 300XL alomost Empty and HP 300 zwart (black) is "gebruikt" (used)
with a ? mark. If I click on that it says "used every day"